Java随笔记 - Java代码实现一个死锁程序

清疚 2022-12-21 06:15 186阅读 0赞

###  Java随笔记 - Java代码实现一个死锁程序 ###

#### 死锁demo ####

*  线程死锁是一个经典的多线程问题，因为不同的线程都在等待根本不可能释放的资源，从而导致所有的任务都无法继续完成。这里就不再赘述理论细节，主要是要用代码简单实现一个死锁的程序，具体代码如下：
    
        // new两个对象用来作为锁
        // 两个方法，方法A先获得obj1的锁，睡眠一秒后，尝试去获取obj2的锁
        // 方法B先获得obj2的锁，睡眠一秒后，尝试去获取obj1的锁
        // 两个方法错开，分别拥有一个锁，再去获取对方手里的锁，就会进入死锁状态
        
        public class DeadLock { 
        
            private Object obj1 = new Object();
            private Object obj2 = new Object();
        
            public void methodA() { 
                synchronized (obj1) { 
                    System.out.println(Thread.currentThread().getName() + " - get the lock of obj1.");
                    try { 
                        Thread.sleep(1000);
                    } catch (InterruptedException e) { 
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + " - to get the lock of obj2...");
                    synchronized (obj2) { 
                        System.out.println(Thread.currentThread().getName() + " - get the lock of obj2.");
                    }
                }
            }
        
            public void methodB() { 
                synchronized (obj2) { 
                    System.out.println(Thread.currentThread().getName() + " - get the lock of obj2.");
                    try { 
                        Thread.sleep(1000);
                    } catch (InterruptedException e) { 
                        e.printStackTrace();
                    }
                    System.out.println(Thread.currentThread().getName() + " - to get the lock of obj1...");
                    synchronized (obj1) { 
                        System.out.println(Thread.currentThread().getName() + " - get the lock of obj1.");
                    }
                }
            }
        
        }
    
        public class ServiceA implements Runnable { 
        
            private DeadLock deadLock;
        
            public ServiceA(DeadLock deadLock) { 
                this.deadLock = deadLock;
            }
        
            @Override
            public void run() { 
                deadLock.methodA();
            }
        }
        
        public class ServiceB implements Runnable { 
        
            private DeadLock deadLock;
        
            public ServiceB(DeadLock deadLock) { 
                this.deadLock = deadLock;
            }
        
            @Override
            public void run() { 
                deadLock.methodB();
            }
        }
        
        public static void main(String[] args) { 
                DeadLock deadLock = new DeadLock();
                Thread threadA = new Thread(new ServiceA(deadLock));
                Thread threadB = new Thread(new ServiceB(deadLock));
                threadA.start();
                threadB.start();
        }